Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 271730

Area Forecast Discussion
National Weather Service Gaylord MI
130 PM EDT Tue Jun 27 2017

Issued at 1032 AM EDT Tue Jun 27 2017

Pretty quiet day in store with minimal updates. Sunny skies at the
moment with just some patchy mid level cloud trying to make it
into NW lower, with increasing higher level cloud coming in from
the north, associated with a weak shortwave trough. Main weather
today, which is not much, will be a relatively high based cu field
developing with some of that higher cloud coming in. Lake breeze
convergence in interior eastern upper and far NE lower will have
most of the cumulus. This is also an area where there is a small
chance for a few showers popping up this afternoon. After
modifying soundings (too high of sfc dew points in model data),
maybe 200-300 MLCAPE/700-900 SBCAPE is revealed, which usually
results in little to no thunder. Left in the possibility for it
across far NE lower. Warmer day than yesterday with highs in the
upper 60s to lower half of the 70s. Warmest readings in
downsloping areas of NE lower.


.NEAR TERM...(Today through Tonight)
Issued at 344 AM EDT Tue Jun 27 2017

...Warmer temperatures today/few lake breeze induced showers???...

High Impact Weather Potential: Minimal.

Pattern Synopsis/Forecast: Midnight composite chart shows a weak
area of low pressure (~1011-1012mb) over southeast Ontario...trough
axis extends south across Lake Huron into northwest Ohio/northern
Indiana.  1021mb high was centered over southwest Minnesota/
northwest Iowa.  Tight/compact vorticity center in water vapor
imagery spinning away from southeast Lower Michigan early this
morning toward the lower Great Lakes...also appears to be a smaller
secondary vorticity center over northern Lake Huron.  Higher
heights/ridging upstream across the Plains.  Band of rain showers in
the process of departing northeast Lower Michigan early this
morning...with clearing skies working into the forecast area from
the north.  Isentropic ascent/warm advection across far northwest
Ontario driving clouds/showers (and some convection) north of Lake

Upstream surface high will ridge southeast into the Ohio Valley least allowing rising pressures and increasingly
anticyclonic low level flow into the upper Lakes.  Low-mid level
warm advection pattern already underway as boundary layer flow backs
more southwesterly overnight as surface high moves into the mid
Atlantic and pressures fall over the plains/Midwest.

Primary Forecast Concerns: Any shower chances along lake breeze
boundaries this afternoon?  Lake breezes expected across Mackinac/
southern Chippewa counties (colliding Lake Superior and Lake
Michigan/Huron breezes?) and probably a boundary hanging tight near
the Lake Huron shore in northeast Lower.  Like we`ve seen over the
past several afternoons...instability will be pretty thin with deep
mixing resulting in a fairly high-based cumulus field.  Better
signal for any precip is across northeast Lower...potentially
stronger convergence along eastern Upper lake breeze can`t be
ignored...but overall probabilities are pretty weak.  Otherwise a
warmer afternoon is on tap for most areas (save for the Alcona/
Iosco/Arenac group of counties where more sun and downsloping west
winds pushed temperatures up around 70 Monday afternoon)...with more
widespread 60s-lower 70s expected this afternoon (though still below
the mid-upper 70s normals for the last week of June).  Dry and
clear/partly cloudy for tonight...with lows in the upper 40s and


.SHORT TERM...(Wednesday through Thursday)
Issued at 344 AM EDT Tue Jun 27 2017

...Heavy rain potential for portions of northern MI Wed night...

High Impact Weather Potential...Heavy rainfall and possibly some
flooding impacts Wednesday evening into Thursday, particularly
across eastern Upper and Tip of the Mitt.

Pattern Synopsis/Forecast...Midlevel shortwave energy that just came
ashore the Pacific Northwest this evening will track across the
northern CONUS, reaching the Upper Midwest on Wednesday. Meanwhile,
surface high pressure will drift from the Ohio Valley to just off
the Mid-Atlantic coast by Wednesday evening, progressively opening
up the Gulf for moisture to surge northward into the Upper Great
Lakes. The eastward tracking shortwave (and another shortwave just
to the north hugging the Canadian border) will interact with this
moisture feed (PWATs approaching 1.8 inches, +1 to 2 standard
deviations) as it induces cyclogenesis over the central/northern
Plains. The resultant more southern surface low is progged to track
from southern MN Wednesday morning through the Upper Peninsula by
daybreak Thursday, though models still vary on its exact track. WAA
and isentropic lift out ahead of this low will overspread northern
Michigan as early as daybreak Wednesday but will strengthen heading
through the afternoon into the evening as a warm front lifts across
the area, settling over eastern Upper Wednesday night. Robust fgen
forcing will accompany this front as it lifts into eastern Upper,
and additional forcing may come into play from the right entrance
region of a 100+ knot upper jet streak. Rain will thus overspread
northern Michigan from SW to NE from mid-afternoon through early
evening. Models have sped up the approach of a SW-NE oriented 50-60
knot LLJ, now showing it nosing into northern MI late Wednesday
afternoon through the evening. Strong moisture transport will
accompany this LLJ with its leading edge tight gradient looking to
take aim anywhere between the Tip of the Mitt and eastern Upper,
which is the expected area of heaviest rainfall. Warm cloud depths
will range from 3.5 to 3.8 km Wednesday evening during the main part
of this event. Nearly saturated columns through the mid levels will
yield nearly moist adiabatic lapse rates. This will lead to MUCAPEs
up to ~700 J/kg (tall/skinny elevated CAPE profiles in forecast
soundings), so there may very well be some embedded thunderstorms
leading to locally enhanced heavy rainfall.

Heaviest rain will depart northeast Lower and far eastern Upper
around or shortly after daybreak Thursday as the LLJ moves east. The
surface low will likely linger over southern Ontario for much of the
day as its associated shortwave aloft shears itself out. So, chances
for scattered showers/storms will linger but gradually diminish
through the day as slightly drier air encroaches from the west.

Due to strong WAA, temperatures will climb into the low to mid 70s
across the area on Wednesday. It will be a tad cooler across eastern
Upper and Tip of the Mitt on Thursday (highs around 70) given a
greater likelihood of lingering clouds and rain there. Across the
rest of northern Lower, temperatures will climb into the mid 70s,
even upper 80s near Saginaw Bay.

Primary Forecast Concerns...Given recent wet pattern across northern
MI, heavy rainfall potential will obviously be the biggest forecast
concern. Expect the LLJ will play the biggest role in producing
heavy rain, so precisely where it orients itself will determine
which area sees the greatest rainfall amounts. Pinpointing that
remains a challenge at this time, and unfortunately there are still
some significant model differences with regard to the intensity,
track, and timing of this system. With the 00Z model run, better
sampling is starting to get ingested into the models now that the
driving shortwave energy has come ashore on the West Coast. Expect
models will start to come into better agreement on the finer details
of this system with today`s subsequent runs.

That being said, confidence is increasing that the heaviest rain
will fall somewhere across a portion of eastern Upper and Tip of the
Mitt, with considerably less rainfall heading south towards Saginaw
Bay. WPC has placed all of northern Michigan under a slight risk for
excessive rainfall through 12Z Thursday. Given recent rainfall and
meteorological factors detailed above, think there will likely be
some rapid runoff into area streams/rivers up there, but plenty of
finer details still need to be ironed out later today.

.LONG TERM...(Thursday night through Monday)
Issued at 344 AM EDT Tue Jun 27 2017

High impact weather potential...Thunderstorms possible Friday and

Thursday night looks to offer a brief break from rainfall across
northern Michigan before another round of rain arrives on Friday. A
frontal boundary will stretch from southern Iowa to the Thumb Friday
morning, and a developing low pressure system is progged to ride
northeast along the front, tracking through northern Michigan Friday
afternoon/evening with another decent shot at a soaking rain,
especially for northern Lower. The first part of the weekend looks
fairly active as well as a cold front slowly drops south across the
area. Sunday is looking dry for much of the area as drier air
filters in behind the front. Some models show potential for rain on
Monday, but confidence is low this far out. Temperatures look to be
near or just a tad below normal through the period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 126 PM EDT Tue Jun 27 2017

...VFR this TAF period...

High pressure crosses south of the srn Great Lakes through the TAF
period, making way for the approach of low pressure and a warm
front by Wednesday afternoon. Cumulus today will gradually
disperse into the evening with mostly clear skies anticipated for
tonight with maybe just some high level cirrus increasing late.
This higher level cloud will thicken through Wednesday with
showers developing Wednesday afternoon and spreading east through
the evening. The rainfall will start to get fairly heavy late in
the afternoon and especially in the evening, especially for PLN.
It will not be until then when CIGS/VSBYS are expected to go


Issued at 344 AM EDT Tue Jun 27 2017

Some lingering gustiness along the northeast Lower nearshore zones
early this morning (primarily between the Straits and Thunder
Bay)...should subside later this morning with some lake breeze
components developing along the Upper Peninsula nearshore zones as
well as along Lake Huron especially from Thunder Bay south this
afternoon.  Winds will become more southwest tonight and increase on
Lake Michigan...with gusty south winds Wednesday likely requiring
Small Craft Advisories within Lake Michigan nearshore zones.




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